Heat treating titanium-base alloy products



Slrenglh x lo psi Aug. 27, 1957 E613 YO00 H. D. KESSLER ET AL HEAT TREATING TITANIUM-BASE ALLOY PRODUCTS Filed Feb. 6. 1956 Yield Strength 0.2 Offset l20 Bhn Sponge Titanium Bose Alloy 6% Al 4%V B00 I400 I500 I600 I700 I800 I900 Solution Heat Treatment Temperolufe, "F

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Harold D. Kessler Russell 6. Shermon JNVENTORS ram Agent United States Patent HEAT TREATING TITANIUM-BASE ALLOY PRODUCTS Harold D. Kessler and Russell G. Sherman, Las Vegas, Nev., assignors to Titanium Metals Corporation of America, New York, N. Y., a corporation of Pennsyl- Vania Application February 6, 1956, Serial No. 563,521

5 Claims. (Cl. 148-115) This invention relates to the heat treatment of titanium alloy products and particularly thin section products.

Titanium alloy bar, sheet and strip products as produced, for instance, by rolling ingots or billets to desired thin section, are often employed to fabricate specific articles by additional forming processes, particularly cold forming. In order to be readily formed by bending, pressing, stretching, cupping, spinning or other fabrication methods, such products must be relatively soft and ductile, and also possess good ultimate tensile strength so that the required deformation can be readily obtained without splitting or other mechanical failures. At the same time it is often desired that the finished formed product show high strength characteristics, which are apparently incongruent with the easy forming properties required for fabrication. Previously obtainable titanium alloy products, if produced so as to be readily formable, have not been strong enough in fabricated form even after the best heretofore known heat treatment; or if produced with actual or potential high strength characteristics have been too hard and strong for proper formability.

It is therefore an object of this invention to provide a titanium alloy thin section product having improved forming properties. Another object of this invention is to provide a titanium alloy thin section product having improved forming properties and which can be subsequently treated so as to possess high strength characteristics. A still further object of this invention is to provide an im proved method for heat treating titanium alloy products. These and other objects of this invention will be apparent from the following detailed description thereof.

This invention, in its broadest aspects, contemplates heat treating of a thin section product, such as for instance bar, rod, wire, sheet or strip, manufactured from a titanium base alloy of the alpha-beta type by rolling, forging, drawing, extrusion, or other conventional methods, and developing superior forming properties in such product by application of a solution heat treatment, within a certain restricted, critical temperature range, followed by a rapid cooling. In this condition the material may readily be fabricated by forming, particularly cold forming. After forming, the product may be subjected to an aging heat treatment to develop high strength characten istics and other desirable mechanical properties.

The term solution heat treatment, as employed herein, is intended to refer, as is generally accepted in this art, to a heat treatment at relatively high temperature to produce a partial solution of the alpha phase and transformation to beta. The rapid cooling (quenching) from this temperature retains at room temperatures substantially the amount and type of beta phase so formed. The aging heat treatment is a generally lower temperature, longer time treatment which normally stabilizes the alloy, which often improves the mechanical properties to some degree, but in the practice of this invention has a surprisingly significant and important effect in substantially raising the low yield strength previously obtained by the particular solution heat treatment employed.

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A clearer understanding of this invention may be obtained by reference to the annexed drawing in which Figure 1 illustrates a typical graph showing the ultimate tensile strength and yield strength (0.2% offset) obtained by solution heat treating at various temperatures and quenching, bar of titanium base alloy useful in the practice of this invention. As is apparent, the ultimate tensile strength curve shown at 10 slopes upward with increase in strength as the heat treating temperature is raised to a peak at 11 after which the curve drops. A very careful investigation of the heat treatment response with respect to yield strength, with determinations made at small increments of temperature difference reveals, however, that at the lower end of the yield strength curve, the curve slopes downward as at 12 reaching a low minimum point at 13, then slopes upwardly as at 14.

Discovery of this phenomenon is of the utmost significance. In the as-rolled condition the rod sample used for the tests of Figure 1 showed a yield strength to tensile strength (YS/TS) ratio of about 0.95. When solution heat treated at a temperature of about 1750 F., this ratio is about 0.85 and both yield and tensile strengths are higher. When heat treated at the temperature of minimum yield point 13, however, tensile strength of 141,000 and the yield strength 99,700 produces the YS/ TS ratio of .71 and the wide dilference between the yield and tensile strength values are apparent. The low YS/TS ratio provides the heretofore unobtainable combination of properties which include the extremely low yield strength to permit easy plastic deformation under minimum load, and a relatively high ultimate tensile strength to prevent fracture, splitting or rupture of the material during such deformation. Another important feature is the favorable response of alloy products produced according to this invention to a subsequent aging heat treatment. The low YS/TS ratio provides excellent forming characteristics, but in addition, after forming, treatment for from 1 to 48 hours at temperatures from 700 F. to 1200 F. substantially improves the ultimate tensile strength, and increases the yield strength tremendously. After this aging treatment a relatively high, more or less normal, YS/TS ratio is produced and the fabricated article is thus provided with most favorable strength characteristics for useful application. The following table shows the strength properties of the alloy of Figure 1 before and after the treatments described.

Titanium base alloys suitable for the practice of this invention are of the alpha-beta type, that is at normal temperatures they are composed of mixed alpha and beta type crystal structure. Essential characteristics of such alloys are:

1. They must contain aluminum generally within the range of from about 0.5% to about 8%. Less than .5% aluminum will not provide sufficient solution heat treatment effect at a temperature far enough removed from the beta transus to avoid grain growth and other undesirable elfects. More than 8% aluminum will raise the strength level of the alloy too high with accompanying danger of embrittlement.

2. They must contain a beta stabilizing element or elements generally within the range of from about 2% to Beta stabilizers which may be employed include molybdenum, vanadium, manganese, chromium andiron. These may be employed singly or in combination. Molybdenum and vanadium employed individually or in com bination are particularly advantageous. 'Less than 2% beta stabilizer will not provide the required .amount of beta phase in the alloy while more than 10% will provide no appreciable gainin desirable properties and since these elements are all heavier than titanium, they will tend to increase the density of the alloy and partially destroy one of the principal advantages of titanium. Incidental impuritie and other elements may bepresent inthe alloys in amounts which do not significantly a'fiect the character or properties thereof. The principal elements present will generally include oxygen, nitrogen, hydrogen,carbon and these should not total more than 0.5%.

It will be recognized that no one alloy or type of alloy will necessarily be best for all applications, and that certain mechanical properties can often be developed to a high degree at the expense of others.

Products composed of alloys containing beta stabilizers within the lower portion of the range, that is from 2% up to about 6%, for example, 6% Al, 4% V; 4% Al, 3% Mo, 1% V and 6.5% Al, 3% Mo, 1% V; when solution heat treated according to this invention will show yield to tensile strength ratios from 0.5 to 0.75. Such products, after aging treatment, will show excellent strength, ductility and elevated temperature properties. Productscomposed of alloys containing beta stabilizers within the upper portion of the range, that is from 6% to 10%, for example, 2% Al, 4% Mo, 2% V; 2% Al, 4% Mo, 4% V; and 4% Al, 6% Mo, 4% V, when solution heat treated according to this invention will show exceptionally low yield to tensile strength ratios generally between 0.25 and 0.6. Such products, after aging treatment, will show good room temperature properties but will not be adapted for elevated temperature service due to the tendency toward instability imparted by the high proportion of beta phase.

The solution heat treating temperature employed to obtain the low yield to tensile strength ratio, according to this invention, appears to be principally dependent on the amount of aluminum present in the alloy. The optimum temperature varies directly with the aluminum content, but is also afiected by the amount of the interstitials, oxygen and nitrogen and possibly carbon present, and, in addition, by the percentage of vanadium in the beta stabilizing elements present in the alloy.

Since the analytical determination of the interstitial elements is long, tedious and often of doubtful accuracy, the gross eifect of their presence is most often determined and measured by the hardness of the titanium sponge from which the alloy is made. Obviously introduction of such elements into the alloy other than by their presence in the sponge will result in the equivalent effect on the optimum solution heat treating temperature and should be considered accordingly. An alloy made from 160 Bhn. sponge, for example, will have an optimum solution heat treating temperature about 20 F. higher than one made from 140 Bhn. sponge, and an alloy made from 120 Bhn. sponge will have such temperature about 20 F. lower than the 140 Bhn. sponge alloy. Higher or lower Bhn. sponge will aifect the critical solution heat treating temperature of the alloy by raising or lowering this temperature about 1 F. for each Bhn. point that the'sponge from which the alloy is made, is higher or lower than 140.

Vanadium appears to affect the critical solution heat treating temperature in a different manner or to a different extent than other beta stabilizing elements. An alloy containing 100% vanadium as the beta stabilizer will have a critical solution heat treating temperature about 50 F. lower than an alloy whose beta stabilizing component is 50% vanadium, and in an alloy containing no vanadium this temperature will beraised50 F. with intermediate proportions in direct ratio. Therefurmllfifiher or lower percentages of vanadium in the beta stabilizing component of the alloy will afiect the critical solution 'heattreating temperature by lowering or raising 'tliis'temperature 1' F. for each percent that the vanadium content of the beta stabilizing elements is respectively above or below 50%.

For practical operation of the process of this invention the range within which the low YS/TS ratio effect may be obtained, may be calculated as follows:

Temperature range F.=1350 to 1450 plus 37.5 multiplied by the percent Al For example an alloy containing 6% aluminum plus *beta stabilizer should be solution heat treated at a temperature between 1350+ 37.5 6= 1575 F. and

assuming that the alloy contained the interstitials oxygen, nitrogen and carbon in amounts corresponding to that which would be present in Bhn. titanium sponge and also that the vanadium content of the beta stabilizers in the alloy was about 50%. If'the alloy was made'from Bhn. sponge and the beta stabilizer content was composed of 3% molybdenum and 2% vanadium, the 1575-1675 F. temperature range would have to be corrected. Since the 160 Bhn. would be 20 points higher than 140, an addition of 20 F. must be made and since the vanadium would amount to 40% of the totalbeta stabilizers, or 10% less than 50%, 10 F. must be added. The corrected range would then be 1615 to 1715 F.

It will be appreciated that the combined elfect of the various types and amounts of beta stabilizers and impurity elements cannot be precisely predicted; the range calculated from the formula will provide an adequate and efiective practical guide.

Table 2, which follows, shows the results ofsolution heat treatment, according to this invention, of a wide variety of products, all made from alloys containing 140 Bhn. sponge except where noted.

The precise minimum point on the yield'strength curve for any alloy may, of course, be readily determined. Samples of the alloy are heat treated at various tempera-- tures, water quenched, and tested in a tensile machine and the ultimate tensile strengths and yield strengths obtained are plotted to obtain curves similar to those shown in Figure 1. The slope of the yield strength curve is relatively steep on-either side of the minimum point; there fore to obtain the lowest possible yield strength to tensile strength ratio it is desirable to heat treat at a temperature at or close to the minimum point, and for best results not more than 50 F. above or below. For practical commercial operation a solution heat treating temperature may be selected by reference to amount of aluminum, vanadium and interstitials in the alloy employed as ex plai'ned hereinbefore. For most efiective treatment, the best temperature within the general or calculated range may be actually determined and the advantages of this invention realized to the fullest extent.

The time required at solution heat treating temperature will depend to a large extent on the thickness of the product being tested. It is necessary that the time of treatment be long enough so that all the material is raised to the desired temperature. In the case of thin sheet and strip, this may be accomplished in 15 seconds and generally not more than A hour, depending on conditions such as type of furnace and rapidity of heating. Electrical resistance heating of individual sheets and strips makes possible rais ing these to the desired temperature in a very short time. often less than a minute, while furnace treatment requires time for the heat to be conducted throughout the material and will take appreciably longer. 'For thicker plate and rods or bars the treatment time may have to be extended to 1-2 hours to insure adequate soaking. In the case of coiled strip, obviously suflicient time at temperature must be given to make sure that even the innermost portions of the coil are adequately heated.

TABLE 2 Solution Heat Treut- Ultimate Yield YS/TS Elong. Red. in No. Product Alloy Composition ment Tensile Strength, Ratio in 1 Area,

Strength 0.2% Ofiset percent percent 1 16;; x W 0.75Al, 4M0, 4V 1,450 F., 1 hr. WQ..-- 112,000 60,000 .53 15 45 ar. 2 .040 sheet. 1A1, 4M0, 4V 1,450 F., M hr. WQ- 116,000 61,000 .52 3 .045 sheet 2111, 4M0, 4V 1, F., hr. WQ 136, 000 60, 500 .44 4 1" x 1" bar.. 2A1, 4M0, 2V.. 1,480 E, 2 hrs. WQ.-. 132,000 70,000 .53 5 .040 sheet 2111, 4Mn 1,50 54 hr WQ 140,000 89, 000 .60 6 .040 sheet.. 2A1. 11%, 4V 1,500 F., hr. WQ" 128,000 ,000 .60 7 .040" sheet 2A1, Zr, 4M0, 4V 1,450 F., 1 hr. WQ.-- 120,000 58,000 .48 8 1%" 2 V 4.4], 3M0, 1V 1,550 F., 1 hr. WQ-.. 144,000 84,000 .58

or. 9 round--. 4A1, 3M0 1,580 F., 6 hr. WQ" 158, 600 117,000 .74 10 .040" sheet 4A1, 2.5Fe... 1,600" F., 54 hr. WQ 151,000 106,000 .70 11"--. W x 45" 4A1, 6M0, 4V 1,550" F., 1 hr. WQ.. 151,000 51,000 .33 12... round... 5A1, 1.6Fe, 1.40r, 1.2Mo (120 1,015 E, 1 hr. WQ 168, 500 90, 500 53 18 37 Bhn Sponge). 13... 16" round... 54113136515, 1.4g1r, 1.2110 (140 1,635 F., 1 hr. WQ 187, 000 102, 400 54 14 16 n onge 14 44" round... 5.415, .6 ie.1.4()3r,1.2Mo (160 1,650 F., 1 hr. WQ. 188,100 108, 500 5B 9 7 1'1 DOIIEO l tl x 6A1, 4V (120 Elm Sp0nge) 1,550 F.,1 hr. WQ- 145,000 103,000 .71 20 51 ar. .040" sheet 6A1, 3M0, 1Fe;-. 1,650 F., V hr. WQ 147, 000 77,000 52 6. 5 .040 sheet. 6A1, 3M0, 2M1! 1,675 F., V, hr. WQ," 120,000 .54 4 W round... 6.5a], )!0, 1V (1 1,600 F., 1 hr. WQ 152,000 104, 000 .68 21 47 1" 111" bar 1,675 F., 2 hrs. WQ-.- 168,000 111,000 .68 19 34 round... 1,725 F., 1 hr. WQ- 165,000 107,000 .65 10 32 )6; x 1,725 F., 1 hr. WQ.- 178,000 45,000 .25 14 19 8!. lyi" at V 8411, 6Cr 1,700 F., 1 hr. WQ.- 160, 000 105, 000 .66 14 38 After solution heat treatment, the alloy product is rapidly cooled, preferably b necessary to retain at room temperature the structure present at the critical heat treating tempertaure. Obviously thick section products cannot be effectively quenched because the heat cannot be e enough from the central portions, and a non-uniform structure will result. In order, therefore, to obtain retenshapes with a minimu y quenched and are considered inches can be adequate-l invent y water quenching. This is alpha-beta Xtracted quickly on to permit rapid and uniform The limits of thickness will vary size and other conditions,

of thin section in the practice of this invention.

It will be appreciated that in commercial operation there may be some delay in quenching due to h products from the heat treating furnaces ing tanks or equivalent app that the material cools appreciab appropriately higher ployed to compensate the products are qucnc according to this invention.

After the titanium base alloy product is quenched, it is in condition for operation may be ca process depending on in shape desired and article, and may invo ning, stretching, drawing, the titanium alloy at this stag dimpling, pres e is characterized by relaandling the allov into the quencharatus. If this delay is such ly before quenching, an furnace temperature should be emfor the intermediate cooling so that hed from the proper temperature heat treated and forming. The forming rried out by suitable apparatus or the nature of the particular change the configuration of the fabricated lve rolling, bending, cupping, spinsing, etc. Since tively low yield strength and relatively high tensile strength, it may rea shapes employing any, operations known in t cracking or other failure.

The formed product is and this is accomplished by between 700 and 1200 about 48 hours followed by air cooling. The higher temperatures within the range noted may temperature, of from about one to then ready for dily be formed cold into a variety of or several, of numerous forming he art without fracture, splitting,

aging treatment heating at comparatively low E, for a period be employed for shorter times, and if the lower aging temperatures are necessary or desirable, somewhat longer time at such temperatures are generally required for equivalent effect. Temperatures below 700 F. will require inordinately long times for proper aging effect and temperatures above 1200 F. will afiect the composition and structure of the alloy too drastically.

As an example of the general effects of aging for various times at various temperatures the following table shows the physical properties of a sample of onehalf inch square bar solution heat treated at 1550 F. followed by water quenching and which was then aged according to this invention.

TABLE 3 [Tl-4Al-3Mo-1V alloy bar (16 square) solution heat treated tor 1 hr. at l,550 F., water quenched and agcd.]

{Forged to sq. bar at 1,650 F.)

Ult. Yield Elong, Red. in

Tensile Strength, Per- Area,

Heat Treatment Strength, p. s. 1. cent Perp. s. i. (0.2% in 1" cent Offset) Solution Heat Treated, 1,550 F.

(1 hr.) WQ 144,000 98, 800 18 47. 1 Aged:

700 F. (2 hrs.) AG 161,000 144, 200 17 43. 5 700 F. (4 hrs) A0. 177, 500 161, 500 11 36.1 106, 000 147. 000 13 55. 4 178, 800 101,000 0 33. 7 174,700 155,000 15 41. 0 177. 200 150, 000 10 32. 8 167, 700 150, 300 13 35. 1 170, 000 143, 800 11 30. 2 178, 400 146, 700 11 32. 1 175, 500 147, 800 12. 5 34. 5 177, 200 154, 300 1 4 l 4. 1 171, 000 151, 200 14 34. 0 175, 000 147, 500 11 39. 8 106, 200 157. 700 15 43. 2 161,800 151,500 15 39. 3 155, 500 148, 500 17 32. 5 153, 000 147, 000 18 38. 2 151, 500 140, 000 18 41. 7 149, 300 145, 700 19 48. 2 145, 000 143, 400 20 40. 4

1 Flaw in gage length. W Q-water quenched; AC-alr cooled.

Aging for 24 hours at 1000 F. will, for all practical purposes, produce a stable alloy composition although the aging time may, if desired and without deleterious effect, be extended to 48 hours. After such aging treatment the product maybe placedin service up to the limit of its applicability, generally not higher than about 800 F., without further change in its physical properties. Aging at lower temperatures, for instance, 800 F. or 900 F., or for shorter periods of time, will generally produce higher strength products as shown by the data in Table 3. While such aged products should not be employed in elevated temperature service, their excellent strength and ductility make them very valuable for specific room temperature applications. The following table illustrates the properties obtained on solution heated and quenched products from Table 1 after heat treating at 1000 F. for 24 hours, with some random examples of treatment also at 900 F.

TABLE'4 Ult. Tensile Yield Elong., Rodin No. Aging Treatment Strength, Strength, Per- Area,

p. s. 1. p. s. i. (0.2% cent Per- Offset) in 1" cent 1 1,000 F., 24 hrs.-- 152,000 134,000 2 900 F. 24 hrs 174,000 161, 000 142, 000 132, 000 154, 000 142, 000 146, 000 141, 000 151,000 129,000 120, 000 121, 000 138, 000 121, 000 123, 000 118, 000 156,000 148, 000 2, 000 148, 700 177,000 158,000 157,000 134,000 0, 000 130,000 170, 000 167,000 177, 500 159, 000 149, 000 147, 000 190,000 171, 000 180,000 164, 000 3 183,000 167, 000 4 157, 000 151, 000 18 40 187, 000 165, 000 12 23 178,000 177,000 10 '14 247, 000 210, 000 4 4 175, 000 170, 000 8 26 It will be noted that the yield strength to tensile strength ratios after aging are all'0.85 or above with most of them above 0.9 compared to the range of .25 to .74 after solution heat treatment.

The work performed on the materialduring the forming operation will affect to some degree its mechanical properties at this stage. All titanium alloys, in common with those of other metals, work harden and this generally results in increasing tensile strength and reduction of ductility.

The cold forming operation, as regards the type and details thereof, intermediate between solution heat treatment and aging, in and of itself form no part of this invention and may be conducted in any manner and to produce any result desired at this stage. It is significant that the overall heat treatment of this invention involves a two step heat treatment; first the solution heat treatment to provide in the material properties which ideally adapt it for cold forming and second a subsequent aging heat treatment to develop an excellent combination of mechanical properties in the formed product.

To demonstrate the. general range and character of the modification of properties during forming, a section of .043" sheet made from a titanium base alloy containing 4% Al, 3% Mo. and 1% V was solution heat treated at 1580 F. for one-half hour, water quenched and then rolled cold to provide a thickness reduction of 5% and l%. This amount of cold working generally corresponds to that provided by industrial forming operations. After cold forming, the specimens were aged for periods from 2 to 48 hours at 800 F. and 1000 F. The mechanical properties obtained are tabulated in Table below.

TABLE 5 [T1-iAl3Mo-1V alloy sheet solution heat treated at 1580 F. for one-ha1f hour, water quenched, cold worked and aged at 800 F. and 1000 F.)

Yield Aging Ult. Tensile Strength Elong. Aging Temp, F. Time, Strength, p. s. 1. Percent Hrs. p. s. i. (0.2 Percent in 2" Offset) 0% OoldWork:

Solution Treated 800 2 8 24 48 2 8 24 48 It will beappreciated'by those skilled in the art that the .yield to ultimate tensile strength ratios shown are illustrative and may vary slightly from the values shown when determined under different conditions. The determination of ultimate tensile and yield strength of different specimens of the same material may produce results which vary within some limits since such mechanical testing is never wholly precise, and differences in speci men treatment and preparation may introduce additional variables. Therefore, it is to be understood that the yield to tensile strength ratios of various products may fall within the ranges specified and are not to be considered as limited for any alloy or type of product to the specific values shown in the tables.

Titanium alloy products are generally produced in the form of rods, bars, plate, sheet, strip, wire, etc. in which form they are sold to fabricators. It is a particular advantage of this invention that thin section products of this type may be produced, solution heat treated and quenched to develop the low YS/TS ratio and this intermediate product sold to fabricators in this condition. Yield strength to tensile strength ratios of 0.75 or below will provide advantageous formability and ratios within the range of 0.75 to 0.25 are readilyobtained according to this invention. The fabricator receives material ideally suited for mechanical workingparticularly cold forming, and after the desired article is shaped or formed a simple aging treatment develops excellent over-all mechanical properties including a normally high yield strength to tensile strength ratio, high strength and good ductility.

Certain titanium base alloy compositions have been disclosed in this application forthe purpose of illustrating the practice of the invention claimed herein. Those containing from 1% to 5% aluminum, and over 6% and up to 10%, in the aggregate, of molybdenum and vanadium are more particularly described and claimed in our copending application Ser. No. 567,720, filed Feb. 27, 1956.

It is to be understood that the solution heat treatment and quenching herein described does not at this stage produeethe best apparently desirable over-all combination of mechanical properties. Heretofore heat treating tempcratures have been selected to give the highest strength properties, both yield and ultimate tensile strength being considered, in combination with good ductility. A later aging treatment has been proposed to stabilize and slightly improve, in some cases, the properties obtained by solution treatment. In contradistinction to this procedure the present invention contemplates solution heat treament within a narrow critical temperature range to provide low yield strength and without particular regard to other properties. The subsequent aging treatment under these conditions has a significant and radical effect, raising the strength level and providing an over-all combination of mechanical properties often equal or better than those obtained by what would have been heretofore considered the best solution and aging heat treatment.

This application is a continuaton-in-part of Serial No. 513,752, filed June 7, 1955, by Harold D. Kessler et al. entitled Heat Treating Titanium-Base Alloy Products," now abandoned.

We claim:

1. A method for solution heat treating a thin section product composed of an alloy consisting essentially of aluminum in amount from about 0.5 to about 8%, a beta stabilizer selected from the group consisting of chromium, iron, vanadium, molybdenum, manganese and combinations thereof in amount from about 2% to about and balance titanium with incidental impurities, which comprises heating said product 'for from about seconds to about 2 hours at a temperature about that at which said alloy shows a minimum point on its yield strength, solution heat treating temperature curve, and rapidly quenching said product from said temperature thereby to provide as a characteristic thereof a yield strength to tensile strength ratio of between 0.25 and 0.75.

2. A method for solution heat treating a thin section product composed of an alloy consisting essentially of aluminum in amount from about 0.5 to about 8%, a beta stabilizer selected from the group consisting of chromium, iron, vanadium, molybdenum, manganese and combinations thereof in amount from about 2% to about 10%, and balance titanium with incidental impurities, which comprises heating said product for from about 15 seconds to about 2 hours at a temperature, in degrees F. within the range determined by the formula 1350 to 1450 plus 37.5 multiplied by the percent aluminum in the alloy said range being corrected by adding or substracting 1 F. for each Brinell point of hardness that the titanium sponge content of the alloy is respectively above or below 140 and by adding or substracting 1 F. for each percent that the vanadium content of the beta stabilizing portion of the alloy is respectively below or above 50%, and rapidly quenching said product from said temperature thereby to provide as a characteristic thereof a yield strength to tensile strength ratio of between 0.25 and 0.75.

3. A method for heat treating a thin section product composed of an alloy consisting essentially of aluminum in amount from about 0.5% to about 8%, a beta stabilizer selected from the group consisting of chromium, iron, vanadium, molybdenum, manganese and combinations thereof in amount from about 2% to about 10%, and balance titanium with incidental impurities, which comprises heating said product for from about 15 seconds to about 2 hours at a temperature, in degrees F., within the range determined by the formula 1350 to 1450 plus 37.5 multiplied by the percent aluminum in the alloy said range being corrected by adding or substracting 1 F. for each Brinell point of hardness that the titanium sponge content of the alloy is respectively above or below and by adding or subtracting 1 F. for each percent that the vanadium content of the beta stabilizing portion of the alloy is respectively below or above 50%, rapidly quenching said product from said temperature thereby to provide as a characteristic thereof a yield strength to tensile strength ratio of between 0.25 and 0.75, and, after an intermediate forming operation, aging said product at for from 1 to 48 hours at a temperature between 700 F. and 1200 F.

4. A thin section product composed of an alloy consisting essentially of aluminum in amount from about 0.5% to about 8%, a beta stabilizer selected from the group consisting of chromium, iron, vanadium, molybdenum, manganese, and combinations thereof in amount from about 2% to about 10%, and balance titanium with incidental impurities, heat treated according to the method of claim 1, characterized by a yield strength to ultimate tensile strength ratio of between 0.25 and 0.75.

5. A thin section product composed of an alloy consisting essentially of aluminum in amount from about 0.5% to about 8%, a beta stabilizer selected from the group consisting of chromium, iron, vanadium, molybdenum, manganese, and combinations thereof in amount from about 2% to about 10%, and balance titanium with incidental impurities, heat treated according to the method of claim 2, characterized by a yield strength to ultimate tensile strength ratio of between 0.25 and 0.75.

References Cited in the tile of this patent UNITED STATES PATENTS 2,754,204 Jafiee et al. July 10, 1956 FOREIGN PATENTS 1,094,616 France Dec. 8, 1954 OTHER REFERENCES Investigation of Heat Treatment of Commercial Titanium Base Alloys, WADC Technical Report 53-26, April 1953, page 2.8. 

1. A METHOD FOR SOLUTION HEATING A THIN SECTION PRODUCT COMPOSED OF AN ALLOY CONSISTING ESSENTIALLY OF ALUMINUM IN AMOUNT FROM ABOUT 0.5 TO ABOUT 8%, A BETA STABILIZER SELECTED FROM THE GROUP CONSISTING OF CHROMIUM, IRON, VANADIUM, MOLYBDENUM, MANGANESE AND COMBINATIONS THEREOF IN AMOUNT FROM ABOUT 2% TO ABOUT 10%, AND BALANCE TITANIUM WITH INCIDENTAL IMPURITIES, WHICH COMPRISES HEATING SAID PRODUCT FOR FROM ABOUT 15 SECONDS TO ABOUT 2 HOURS AT A TEMPERATURE ABOUT THAT AT WHICH SAID ALLOY SHOWS A MINIMUM POINT ON ITS YIELD STRENGTH, SOLUTION HEAT TREATING TEMPERATURE CURVE, AND RAPIDLY QUENCHING SAID PRODUCT FROM SAID TEMPERATURE THEREBY TO PROVIDE AS A CHARACTERISTIC THEREOF A YIELD STRENGTH TO TENSILE STRENGTH RATIO OF BETWEEN 0.25 AND 0.75. 